Genome-Wide Associations with Flowering Time in Switchgrass

Switchgrass is an emerging bioenergy crop and perennial grass native to North America. Improving biomass yields is critical for developing switchgrass into an economically viable crop. Flowering time has a major effect on biomass yields as delaying flowering time prolongs the period of vegetative growth, in turn, increasing biomass. However, delayed flowering also increases susceptibility to winter mortality which decreases productivity in following years. As such, elucidating the genetic control of flowering time will help breeding efforts and the development of resources for improvement of switchgrass yields. Here, we use exome-capture genotypes at 1,377,841 SNPs in 509 switchgrass individuals to identify associations with heading date measured over three years. There is strong population structure in the sample set, and we perform GWAS on several subsets of samples to identify genic regions that may play a role in controlling flowering time. Several associations are in regions containing homologs of genes with important roles in phenological and circadian regulation in other species, suggesting they have a conserved function in switchgrass.  Our results advance the understanding of flowering time regulation in switchgrass and will inform future work to improve switchgrass biomass yields.